Furnace



Patented Jan. 5, 1932 UNITE o srA' Es' WILLIAM A. GILciin isT, or cHIcaeo; rmi'nois' FURNACE Continuation of applfiationSerialNo. 587,193, filed Septemberfi, 1922.",v This application filed October 14, 1927. Serial naaeaasi.

This application is acontinuation of my.

application for a patenton a Furnace and method for burning fuels of lowheat value for industrial purposesvfiled September), 1922, bearing Serial Number 587 ,193. i

This invention relates to the'burning of fuels such as bagasse, saw dust and other fuels having a large moisture content and,

having a large proportion of volatile .com-. bustibles. y

One of the objects ofthis inventlon le to provide a furnace for burning the above and similar fuels with improved eificiency, this improvement being obtained by provldmg 3 refractory walls which will absorb heat from the burning volatiles and reflect it back. upon the solid fuel. v I

Another object of this invention is to pro vide an improved furnace for burning fuels. I such as the above described fuels and having the complete combustion of all of the come bustible volatilesissuing from the fuel.' I I Other objects, advantages, and capabilities are inherently possessed by this invention and will later appear.v -The drawings l which illustrate the invention show but one embodiment thereof and therefore it should be understood that the invention comprehends other modifications whichare included within the scope of the appendedlclaims.

Referring now to the drawings Fig. 1 :is'a central vertical longitudinal section of a furnace constructed in accordance with this in-r vention. Fig. 2 is a central vertical; central section of a Slightlymodified form of the in vention. V a

In carrying out the improved method recognition and advantage are taken ofthe fact that the principal source of heat tobe ;derived from the burningof. low grade'solid fuels containing considerable amounts of moisture is the combustion of the volatile constituents of thefuel' after they have left the fuel bed, Also that heat, in addition .to

that obtained by the combustion of thefixed carbon, must be suppliedto the fuel bed to promote drying and destructive distillation. If this is notdone the fuel will only smolder with theobjectionable production of smoke and it will not only beimpossible to burn a sufficient quantity of the fuel to obtain a useful resultbut'much of the heat which should be derived from that fuel which is consumed,

is lost byinconiplete combustion of the gases.

It will, of course, be understood that the requirement for supplying additional heat to the fuel bed arisesfrom the factthat the drying and destructive distillationof the fuel are both heat absorbing reactions while the proportion of fixed carbon contained inthe fuels employed is so low that the generation of any considerable amount of heat by com I bustion occurring within the fuel bed is not to be expected. Furthermore, no advantage canbe obtained by direct radiation of heat from the fuel bedonto the boiler shell or other part to be heated. On the contrary, better resultsare secured if provision is made for preventing direct radiation of heat from the fuel bed. It then becomes possible to maintain a higher furnace temperature and this is desirablefor the reason that drying and'destructive distillation of the fuel proceedmore rapidly andthe combustion of both fixed carbon and volatile constituents is more active.

In the drawings a fire box chamber 10 is providedjwith a wide open rear end communicating with the combustion chamber 11. The

rear wall 12 of the combustion chamber is Y constructed of refractory material which becomes heated by the burning gases to a state of lncandescence and Hi this state reflects and radiates alarge amount of heat forwardly through the burinnngases onto the rearwardly exposed face of the fuel bed 13. The fuel bed is supported on a grate 14 which may or may not be inclined, but it is important that the fuel be supported in sucha manner that it presents a relatively long rearwardlv facing both figures of the drawings. The fuel is fed into the grate through the feed hopper 15.

Above the fuel is located the roof or arch, a. portion 16 of which is here shown as being horizontal, but of course this portion may be inclined if desired.

Extending rearwardly from the fuel to the rear wall of the combustion chamber is a refractory floor 17. This floor is found to aid considerably in the increase of furnace temperatures by reason of the fact that it radiates and reflects a large amount of heat upwardly into the burning gases and upwardly against the downwardly inclined arch. If desired this floor 17 may be raised somewhat above the lower edge of the grate so that the fuel will pile against the shoulder 18 and be prevented fromflowing onto the floor.

The heat produced by this fuel used to heat a boiler 19 asshown in Fig. 1 but of course some other heat absorbing device might be employed.

The heat reflected forwardly and upwardly by the floor 17 is caught on the downwardly inclined arch 20 and reflected and radiated by this arch forwardly and downwardly on the fuel surface. The majority of this heat transmitted by the arch is received by the upper portion of the fuel bed where the moisture is present in the largest quantities. On being driven off, this moisture will arise from the fuel bed and whenever it strikes the highly heated arch 20 its temperature is greatly increased and it is compelled to give off any volatile combustibles which may have been absorbed by the water vapor. None of this water vapor can escape through the flue without passing through the highly heated zone in the combustion chamber because. as the gases pass downwardly over the arch, they are pushed down into the combustion chamber by the nose 26 of the arch whereby they are directed into the highly heated portions of the combustion chamber.

The gases flowing out of the combustion chamber then pass through the horizontal heating fine '21 of the furnace as shown in Fig. 'l. or the vertical flue provided between the vertical tubes and the refractory wall 25 as shown in Fig. 2. The refractory wall 24 in Fig. 1 not only supports the boiler but also aids in maintaining the furnace temperatures. In the furnace shown in Fig. 2 the products of combustion pass between the vertical tubes 23 and outwardly through the flue 22.

The type of fuel for which this furnace is intended does not burn principally in solid state but is of such a character that in the presence of heat it gives off a large amount of combustile gases which upon being burned produce more heat than is produced by the remaining solids. The furnaces which have hitherto been used have not been adapted to drive off these combustible volatiles efliciently and also to burn these volatiles completely after they have been driven off. Some of the previous failures have been due to the fact that the moisture in these fuels was not separated from the fuel except at the same time that the combustible volatiles were, in many cases the water vapors were allowed to carry off with them a large proportion of the combustible volatiles and in still other cases the cool water vapors, though having no heat value, where permitted to accumulate in cold spots in the furnace or to otherwise flow through the furnaces in such a way as to reduce the furnace temperatures.

This invention provides in a furnace several refractory walls which have different functions, all of them cooperating to produce a new result in the burning of these fuels. The combustion chamber is in wide open communication with the fire box in which the fuel reposes. As the combustible gases'hurn in the combustion chamber 11 they not only transmit heat directly to the fuel but they transmit a large amount of heat to the rear well 12. It is found that this wall attains a state of high incandescence and that it reflects and radiates the heat received by it back through the burning gases, thereby increasing their temperatures and also through those gases upon the rearwardly facing surface of the fuel. Since the moisture has been to a great extent evaporated from the fuel as it progresses downwardly from the top of the heap the lower portions of the fuel heap are well dried and are perfecly adapted to give' off the combustible volatiles which they contain.

At the same time the refractory floor 17 lying underneath these hot gases also receive a large amount of heat from the gas and reflects and radiates the heat upwardly thereby sustaining and increasing the high temperature of the gases. Because of the efficient reflection and radiation from these walls and floor and from the side walls of the furnace it is found that the combustible gases attain temperatures higher than those hitherto attained in the burning of these fuels. These exceptionally high temperatures are necessary to promote complete combustion of these gases. The enlarged combustion cham ber has ample space for retaining the combustible gases at the rate which they are produced until their combustion is substantially completed.

The combustion of these volatiles not only heats the floor. the rear and side walls, but it also gives off a great deal of heat to the downwardly inclined arch 20. This arch is placed close to the fuel surface so that it may radiate and reflect heat upon the fuel surface with the utmost practical efficiency. The heat received by the fuel from this arch is found to drive off most of the water vapor from the fuel in the upper part of the bed and hence before the fuel reaches the bottom portion of the bed it has become well dried. When this water vapor is evaporated from the top of the fuel pile it is not permitted to escape to the exhaust flue without being subjected to the intense heat in the combustion chamber. It must not only pass down in front of the highly heated refractory arch 20 but-it must also flow down past the nose 26 of the arch to become mixed with the burning gases in the combustion chamber. In this i'nanner the water vapor is compelled to give off any combustible volatiles which it'may be carrying. The various refractory surfaces provided in this furnace therefore cooperate to extract from these low grade fuels every particle of combustible matter they contain, and when used in accordance with the foregoing disclosure will burn these fuels with an efiiciency not heretofore attained.

Havingshown and described my invention I claim: j

1. In a furnace, in combination, a rearwardly facing inclined grate, means for feeding fuel to the upper edge of the grate and refractory walls enclosing an unobstructed common fire box and combustion chamber having the said grate located at its forward end and an exit flue opening at the upper rear corner thereof,.the said refractory walls comprising an upwardly facing floor extending rearwardly fromsubstant-ially the lower edge of the grate, a vertical rear end wall extending upwardly from the rear edge of the said floor to one side of the said exit flue opening and a roof extending horizontally rearward over the grate from the plane of the front end thereof and thence obliquely downward and rearward to the other side of the said exit flue opening.

2. In a furnace, in combination, a rearwardly facing inclined grate, means for feeding fuel to the upper edge of the grate and refractory walls enclosing an unobstructed common fire box and combustion chamber having the said grate located at its forward end and an exit flue openingat the upper rear corner thereof, the said refractory walls comprising an upwardly facing floor extending rearwardly from substantially the lower edge of the grate, a vertical rear end wall extending upwardly from the rear edge of the said floor to one side of the said exit flue opening and a sloping fire box roof facing the grate with its rear edge constituting the other side of the said exit flue opening;

3. In a furnace, a fuel chamber and means therein for supporting a bed of fuel to provide a rearwardly facing exposed surface of fuel. a refractory arch extending rearwardly and downwardly at the top of the fuel chamher, said arch facing the rearward surface of the fuel and being adapted to reflect and radiate heat upon the upper half of said surface, and an enlarged combustion chamber extending rearwardly of the fuel surface and having arefractory wall adapted to radiate and reflect heat forwardly through the chamber below said'arch against substantially the entire lower half of the fuel surface, said arch being adapted to deflect rearwardly flowing combustible volatiles aising from the fuel downwardly in front of said refractory wall.

In a furnace, a fuelchamber and means therein for supporting a bed of fuel to provide a rearwardly facing exposed surface of fuel, arefractory arch above said fuel extend:

ing rearwardly and downwardly, an enlarged combustion chamber extending rearwardly of the fuel and fuel chamber of capacity ample for retaining and retarding rearwardly of the fuel a large volume of the combustible volatiles emanating from the fuel duringtheir combustion,said combustion chamber having a rear refractory wall extending upwardly substantially vertically and facing said fuel, said arch being shaped to radiate and reflect heat forwardly and downwardly upon the upper halfof said fuel surface and to deflect the rearwardly flowing volatiles downwardly into the combustion chamber in front of said rear wall, said rear wall being constructed and shaped to radiate and reflect heat re-- ceived from the retained burning volatiles forwardly through all the gases retained in the combustion chamber and onto the lower half of said fuel surface.

In a furnace, a fuel chamber and means therein for supporting a bed of fuel to provide a rearwardly facing exposed surface of fuel, a refractory arch above said fuel extending rearwardly and downwardly, an enlarged combustion chamber extending rearwardly tion chamber under said arch onto the lower half of said fuel'surface, said combustion chamber having a refractory floor extending rearwardly from the rearmost surface of the fuel to said upwardly extending wall and having an exhaust flue rearwardly of saidarch leading from the upper rear portion of the chamber.

6.111 a furnace, a fuel chamber and means .therein for supporting a'bed of fuel to present an inclined rearwardly facing exposed surface of fuel, an enlarged combustion chamber extending rearwardlyfroin the fuel and the fuel chamber having an upwardly extending transverse refractory wall facing the fuel, a refractory arch forming aroof above the fuel and steeply inclined downwardly and rearwardly with its lowermost portion sufliciently high to permit of radiation of heat from said transverse wall forwardly thereunder against the lower half of the exposed fuel surface, said portion being positioned to deflect gases flowing along the arch downwardly into the central portion of the combustion chamber, a fine opening between the rear end of said arch and said transverse Wall, and a refractory floor extending forwardly from said transverse wall to the fuel bed, said combustion chamber ha ing ample capacity for retarding and retaining therein a large Volume of the vo atilc combustibles emanating from the fuel.

In Witness of the foregoing I aflix my signature.

WILLIAM A. GILOHRIST. 

